Solid State and solution nuclear magnetic resonance spectroscopy has been used to study the structure of peptides in various noncrystalline states which may be similar to the physiological environment. The peptides we have studied include a series of peptides which is a part of the integral membrane protein, gp4l, found at the surface of human immunodeficiency virus. As a result of these conformational studies we have identified transmembrane regions as well as other regions which interact exclusively with the phosphate polar headgroups of the membrane bilayer. We have also studied the solution structure of two peptides associated with a region of the gp4l. One peptide is highly antigenic and distinguishes between the sera of healthy HIV positive patients from those with AIDS. The corresponding peptide where alanine is replaced by threonine in position seven does not show such a distinction. We have also developed new NMR pulse methods for studying these systems and we are continuing to evaluate the errors in the corresponding measurements. We have developed and implemented new NMR pulse methods for studying these systems and we are continuing to evaluate the errors in the measurements.